I have the greatest respect for gymnasts, because they are basically top of the heap for pound for pound strength. It's not an area of expertise for me though, so please enlighten me: if using momentum to get a kipping muscle up and then gradually reducing the momentum assist until you can do it strictly isn't the right progression, what is?
I think the main problem with the Crossfit-kipping-approach you often see on YouTube is that it doesn't look like the person being filmed is at all interested in ever transitioning to a proper muscle up, but rather to kip as much as possible to get as many reps as possible in 60 second or w/e.
You're absolutely right in that you need to start somewhere, and a properly instructed kip can definitely help there. But you could also start by doing negatives of the partial exercises (start pulled/pushed up and lower yourself down in a controlled manner), which can be at the same time used to teach proper form and naturally transition into a full muscle up.
Once again, it's the classic Crossfit problem: if you do it properly and controlled, it is a nice exercise regimen. According to most anecdotal evidence, a lot of people don't, though.
Edit:
retiredcoder also replied with bands etc. to support in the beginning, which is obviously also a good method and, now that I think of it, one I've often seen in my gym. In the same vein, there's usually a pull up machine somewhere in the back that will support you by using a counterweight on the way up, though here you'll have the usual discussion regarding machine/no machine.
One thing to consider when scaling down and up an exercise is to measure progress, kipping is not very precise and usually used to make one achieve arbitrary goals way off ones reach (eg massive ammounts of pull-ups in a short period of time, oh impossible even for elite athletes but with kipping we can get there).
Same goes with handstand push-up with against the wall and that kick up. That’s one of the hardest exercises in gymnastics from my experience, why do one want to do that in a HIIT is beyond me.
As for scaling, I never consider not compromising but actually reinforcing proper form even overthinking it, to prepare one for load and speed (when things tend to go awry). As tools and techniques to scale down, there are bands, eccentrics, Grease the groove, etc.
Ps: you seem to have been downvoted but your question seemed legit to me. I hear that a lot from gym mates
The right progression is breaking the muscle up into its separate components and getting strong at each one individually until you can combine them into one movement and do your first muscle up.
You have to accept that it will be a long time before you can do even one proper muscle up, and most people just aren’t willing to so they kip and tell themselves they can do “muscle ups”.
A lot of bodyweight exercises, muscle ups included, have a strong technique component. Kipping teaches bad habits that you need to unlearn to learn a "real" muscle ups.
